A model helps scientists form testable hypotheses. what hypothesis was being tested with the δfus3 strain? what hypothesis was being tested with the δfus3 strain? fus3 is required for the signal transduction pathway leading to shmoo formation. fus3 is required for formin phosphorylation. fus3 causes shmoo formation in mating yeast. mating factor is required to start the signal transduction pathway leading to shmoo formation.